This invention is directed to a cryogenic refrigerator, and particularly a Vuilleumier refrigerator having a pneumatically operated cold displacer.
The original Vuilleumier refrigerator was disclosed by Rudolph Vuilleumier in U.S. Pat. No. 1,275,507. He defined a structure wherein displacement of the gas in the system between volumes at different temperatures caused pressure changes and the pressure changes in turn achieved heat cycle purposes. The Vuillemumier refrigerator was adapted for minaturization by K. W. Cowans in U.S. Pat. No. Re. 27,338. A further improved structure, of greater efficiency was taught by G. P. Lagodmos in U.S. Pat. No. 3,742,719. Thus, the background includes teaching that pressure changes can be accomplished by moving refrigerant gas from one chamber to another to achieve heating and cooling. Furthermore, cycling of the refrigerant gas causes gas expansion in the space to be refrigerated, with the achievement of refrigeration. In the usual Vuillemumier structure, as evidenced by the Cowans and Logodmos patents, the hot displacer and cold displacer have been mounted in the same structure in order to achieve cyclic interrelationship so that mass transfer and heat transfer are accomplished to produce the refrigeration.
The background also includes Higa U.S. Pat. No. 3,367,121. Higa teaches in his FIG. 3, which is not an immediately apparent part of his disclosure, that the Stirling Cycle can be modified to have a separate cold cylinder in which refrigeration is produced, with the connection of the cold cylinder to the rest of the refrigeration equipment only through a single line. The line provides pressure pulses which cause reciprocation of the cold piston. The Stirling Cycle has the disadvantage that pressure seals are required in the pressure pulse generating equipment. Such seals wear and tend to lose effectiveness to reduce the life of the equipment.